Sound detecting test apparatus



a wwv Jan. 30, 1968 H. J. KANE SOUND DETECTING TEST APPARATUS 2Sheets-Sheet 1 Filed Oct. 13, 1966 FIGZ.

INVENTOR.

id z orraemsy Jan. 30, 1968 H. J. KANE SOUND DETECTING TEST APPARATUS 2Sheets-Sheet 2 Filed Oct. 15, 1966 Iilliw iL ax m5 1 M Cir, Q mm p 53 aM \N\LS K F ;\..J W M M t 1% m Q 4/ v 01 T United States Patent3,365,935 SOUND DETECTING TEST APPARATUS Hubert J. Kane, Baker Lane,Andover, Mass. 01810 Continuation-impart of application Ser. No.344,714, Feb. 13, 1964. This application Oct. 13, 1966, Ser. N0. 586,416

10 Tl-aims. (Cl. 7371.4)

This application contains subject matter identical to that disclosed inmy co-pending US. patent application Serial No. 344,714 filed February13, 1964, and now abandoned and constitutes a continuation-in-partthereof.

The present invention relates generally to improvements in testapparatus and it relates particularly to an improved device foridentifying and locating defects and sources of malfunctioning ofequipment possessing enclosed moving parts or moving media by the sonicexamination and survey thereof.

In industry many forms of equipment are employed which contain numerousenclosed moving parts and moving media. Typical of this equipment areinternal combustion engines such as diesel engines, gasoline engines andother prime movers, hydraulic and pneumatic systems and the like. Undernormal operating conditions equipment of the above type generate a soundpattern of a tone, quality and intensity which is characteristic of theparticular piece of equipment. Any significant variance from thischaracteristic sound pattern generally indicates a malfunctioning anddefect in the equipment and such a variance is often easily recognizableby an operator or attendant who is familiar with the equipmentsoperation. However, while the malfunctioning is readily apparent, thecause of such malfunctioning is frequently difiicult to isolate andidentify even by the expert. While a deviation from the normal frequencydistribution and intensity of the sound pattern generated by the overallequipment is an index of its malfunctioning, such as caused by a worm ordefective part, a misadjustment, the presence of a contaminent ordeleterious deposit or a defect in a moving medium, this deviation, assuch, does not identify the precise locus or source of themalfunctioning. Since the operating equipment generally generates manysounds of various natures at different parts of the equipment and theseparts are in good mechanical sound communication, such individual soundsare merged into a common pattern so that difficulty is encountered inisolating particular sounds and identifying them as to their sources,and in assigning a change in the overall sound pattern to a specificarea.

Many devices and procedures have been employed and proposed forexamining the sound pattern of equipment in diagnosing anymalfunctioning thereof. However, these devices and procedures possessmany drawbacks and disadvantages. It has been a common expedient to usea stethoscope in an attempt to identify and isolate abnormal operatingsounds as an indication of a defect in equipment. While such expedienthas some applications, its use is highly limited since, although itpermits improved sound resolution, it merely presents the sound patternof the overall machine. It has been discovered that a closed comparisonof the sound patterns, occurring substantially simultaneously or inclosely spaced relationship at different parts of the equipment undertest, provides extremely valuable data in connection With the locus orcause of a malfunctioning and usually permits the inspector to promtplyisolate the defect. The frequency distribution and intensity of thesound pattern enters into comparison and such comparison may be audiblyeffected such as by the use of listening devices or visually by means ofsound level meters or oscilloscopes in accordance with the procedureafforded by the present invention.

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It is, therefore, a principal object of the present invention to providean improved test apparatus.

Another object of the present invention is to provide an improvedapparatus for detecting the cause of a malfunction in equipmentcontaining numerous enclosed moving parts or moving media.

Still another object of the present invention is to provide an improvedapparatus for effecting a comparison of the sound patterns at differentsections of enclosed moving part equipment as a guide to the cause orlocus of any malfunctioning of the operating equipment.

A further object of the present invention is to provide an improvedapparatus for analyzing the operation of an internal combustion engine.

Still a further object of the present invention is to provide animproved apparatus of the above nature characterized by its ruggedness,compactness, convenience, versatility and ease of operation.

In a sense the present invention contemplates the provision of a testapparatus comprising an audio amplifier including an input and anoutput, a plurality of remotely located audio pickups, a coupling deviceafiixed to each of said pickups for releasably mounting said pickups toequipment under test, means including a switch for alternativelycoupling selected individual pickups to said amplifier input, and atransducer coupled to the output of said audio amplifier.

According to a preferred form of the present apparatus, there isprovided a portable case in which the amplifier and other components arehoused and which is provided with a rear door providing access to astorage space within the case. The front or face panel of the casecarries a multicontact rotary switch and a plurality of first socketsselectively alternatively connected by Way of the rotary switch to theamplifier input. Each of the audio pickups include a permanent magnetfor releasably mounting the pickup to different parts of the equipmentunder test and a coupling cable terminating in a plug engaging one ofthe respective first sockets. Also mounted on the face panel is acurrent meter connected across the amplifier output through a capacitorand rectifier. Second sockets are located on the face panel andconnected to the amplifier output and earphones are coupled to thesesockets. There is provided a microphone and a switching arrangement forselectively connecting the microphone or a pickup unit to the amplifierinput permitting its selective use as an intercommunication system. Inaddition there are included a volume control network and a tone controlnetwork including adjusting knobs located in the face panels, andamplifier output terminals permitting the connection of an oscilloscopeor recording device.

Additional objects and advantages of the invention will become apparentduring the course of the following specification when taken inconjunction with the accompanying drawing, in which:

FIG. 1 is a front elevational view of an apparatus embodying the presentinvention with a pair of audio pickups shown coupled thereto andattached to different portions of a hydraulic system, which is shownfragmentarily;

FIG. 2 is a sectional view taken along line Z2 of FIG. 1 with the rearlid shown in partially open condition;

FIG. 3 is a view similar to FIG. 2, the apparatus being shown in apartially disassembled condition;

FIG. 4 is an enlarged section view taken along line 44 of FIG. 1;

FIG. 5 is an elevational view, partially broken away, of another form ofpickup member employed in the present apparatus and FIG. 6 is aschematic diagram of the circuit network of the present apparatus.

Referring now to the drawings which illustrate a preferred embodiment ofthe present invention, the reference numeral generally designates theimproved apparatus which includes a portable casing 11 which houses thecircuit network forming part of the apparatus and provides an easilyaccessible storage space for the various apparatus accessories. Thecasing 11 comprises a rectangular bottom wall 12 provided with footpieces 13 depending from the corners thereof and having a vertical lip14 along its front edge and an upwardly rearwardly directed flange 16along its rear edge. Affixed to the top face of the bottom wall 12immediately rearward of the lip 14 is a transversely extending anglemember 17 having a vertical leg delineating with the lip 14, atransverse locking groove. Trapezoidal vertical side walls 18 aredisposed along the side edges of the bottom wall 12 and have forwardlyupwardly inclined rear edges.

Extending between the upper edges of and integrally formed with the sidewalls 18 is a forwardly upwardly inclined top wall 19, the forward edgeof which terminates in a rearwardly downwardly inclined bezel definingflange 20 which joins inwardly rearwardly inclined bezel flanges 21formed along the front edges of the side walls 18. A transverselyextending angle member 22 is aflixed to the underface of the top wall 19and includes a depending leg spaced shortly rearwardly of the free edgeof the bezel flange 20 and directed toward the vertical leg of the anglemember 17. The assembly of the bottom wall 12 to the side walls 18 iseffected by the provision of a pair of angle members 23 affixed to theinner lower borders of the side walls 18 and a pair of angle members 24aflixed to the inner rear borders thereof, the angle members 23 and 24having inwardly directed legs adjacent the corresponding edges of thewalls 18. The bottom wall 12 is secured by screws to the angle members23 and the flange 16 is secured by screws to the lower sections of theangle members 24.

A rectangular intermediate panel 26 extends between the casing top andbottom walls 19 and 12 and divides the casing into a rear storage area28 and a front circuit and component housing area 29. The upper borderof the intermediate panel 26 engages the depending leg of a transverselyextending angle member 30 affixed to the under face of the top wall 19.Projecting forwardly of and affixed to the side borders of theintermediate panel 26 are a pair of opposite guide channels 32 havingfront flanges 33 in alignment with the vertical legs of the anglemembers 17 and 22 and closely spaced rearwardly of the free edges of thebezel flanges 21. Access to the storage space 28 is provided through adoor 34 hinged along its lower edge to the upper edge of the flange 16and swingtable between a closed position registering with the rearopening to the storage space 28 and in engagement with the angle members24, and an open position. A permanent magnet latch 36 is aflixed to thebottom rear border of the top wall 19 and engages the upper border ofthe door 34 when the latter is in its closed position to releasablymaintain the door 34 in such closed position. The door 34 is formed of amagnetically-permeable material, such as steel. A handle 37 is afiixedto the upper outer face of the door 34 to permit the opening and closingthereof and a handle 38 is affixed to the upper face of the top wall 19to facilitate the carrying of the apparatus 10.

The various electrical components of the test apparatus are mounted on arectagular front wall or face panel 39, the upper border of which isentrapped between the angle member 22 and the free edge of the bezelflange 20, the side borders of which are disposed between the channellegs 33 and the free edges of the bezel flanges 21 and the bottom borderof which is entrapped between the angle member 17 and the lip 14. Themethod of assembling the casing 11 is clear from a view of FIGS. 2 and 3of the drawings. A power supply battery B is releasably supported on therear face of the intermediate panel 26 by a bracket 40.

The electrical network forming part of the present apparatus includes athree stage DC coupled wide band transistor amplifier 41 powered by thebattery B and corn prising three transistors T1, T2 and T3 respectively.The positive terminal of the battery B is connected to a positive line31 and the negative terminal is connected through a switch S1 to agrounded negative line 35. The collector of the input transistor T1 isgrounded and the emitter thereof is connected to the positive line 31through a resistor R1 and to the base of the transistor T2. Thecollector of the transistor T2 is grounded and its emitter is connectedto the base of the transistor T3. The emitter of the transistor T3 isconnected to the positive line 31 through a resistor R2 shunted bycapacitor C1.

in order to selectively alternatively couple one of a plurality ofanalyzing audio pickups or a microphone to the input of the amplifier 41as defined by the base of the transistor T1, there is provided amulticontact rotary selector switch S2 and a double pole double throwswitch S3, which switches are mounted on the face panel 39, the switchS2 being controlled by a panel mounted knob 42. Also mounted on the facepanel 39 are a plurality of first socket members 43 each having agrounded outer terminal and an inner terminal connected to a respectivecontact S2]; of the switch S2. The switch S3 includes a pair of gangedswitch arms 53a and 83b each cooperating with a corresponding pair ofcontacts S3a1 and S3a2, and S3b1 and S3122 respectively. The switchcontact 83:11 is connected through one or more microphones 45,preferably carbon microphones, to ground by way of suitable couplingcords and plug and jack arrangements and the switch contact S3b1 and theswitch arm S3a are connected through a common resistor R3 to thepositive line 31. The switch contact S3b2 is connected to the selectorarm 52a of the switch S2 and the switch arm S31) is connected throughthe resistance element of a volume control potentiometer P to ground.The control arm of potentiometer P is connected through a blockingcapacitor C2 to the base of the transistor T1 which base, in turn, isconnected through a resistor R4 to the positive line 31. The batteryswitch S1 is ganged with the potentiometer P in the usual manner andboth are controlled by a face plate mounted knob 44. The positive line31 is connected through a capacitor C3 to ground.

The output of the amplifier 41 and specifically the collector of thetransistor T3 is connected to ground through a resistor R5 connected inseries with one or more parallel connected earphones 46. The earphones46 are coupled into the circuit, as aforesaid, by means of one or morecorresponding face panel mounted socket members 47 and mating plugsconnected to the earphones 46, the sock et members 47 being connected inparallel between the resistor R5 and ground. A sound level current meterM has one of its terminals connected to ground and its other terminalconnected in series with a first diode rectifier D1 and a blockingcapacitor C4 to the collector of the transistor T3. A second rectifierdiode D2 oriented oppositely to the diode D1 grounds the junction pointof the diode D1 and capacitor C4. A pair of binding posts 48 and 49respectively are mounted on the face plate 39, the binding post 49 beinggrounded and the binding post 48 being connected through a blockingcapacitor C5 to the collector of the transistor T3. The binding posts 48and 49 may be selectively connected to an oscilloscope, a recordingoscillograph or other desirable visual signal indicating or recordingdevice.

A tone control network is associated with the output of the amplifier 41and includes a multicontact rotary selector switch S4, the selector armof which is grounded and the contact elements of which are respectivelyconnected to the terminals of a group of filter capacitors C6 ofsuccessively larger capacitance. The other terminals of the capacitorsC6 are connected to the transistor T3 collector. The selector switch S4is controlled by a knob 50 on the face panel 39. In order to test theadequacy of the battery B, a normally open push button switch S ismounted on the face panel 39 and is connected in series with amultiplier resistor R6 between the positive line 31 and the ungroundedterminal of the meter M. Closing of the switch S5 will cause a fullsweep of the pointer on meter M, indicating that the battery B isactive.

Referring to FIGS. 1 and 4 of the drawings in which is illustrated oneof a plurality of audio pickup members which form part of the presentapparatus, the reference numeral 51 designates the novel pickup whichincludes a rectangular housing 52' having a bottom wall 53. The meansfor releasably attaching the pickup 51 to a magnetically-permeablesection 54 of the equipment under test comprises a strong permanentmagnet 56 formed of Alnico, a ceramic magnetic material or the like. Themagnet 56 is formed with four fiat-faced segmental legs 57 serving aspole sections and connected by a bridge section 58. The provision ofthese four legs 57 provides firm adherence of the magnet 56 to a curvedsurface such as a pipe, preventing slippage. The bridge section 58 abutsthe outer face of the housing wall 53 and is firmly affixed thereto byabolt 59 provided with a mating nut 61. The bolt 59 extends through astud-shaped assembly of disks of heat-insulating material 55 whichserves to protect the sensitive sound pick-up components, as will bepresently explained.

Located in the housing 52 and spaced from the walls thereof is asound-to-electrical signal transducer 60, advantageously a standardcrystal type photograph pickup, as illustrated, in which the crystalelement is housed in a metal casing. The transducer 50 is provided inthe conventional manner with a needle-receiving drive armature (notshown), and is supported in the housing 52 by a drive member 62preferably in the form of an L-shaped strip of resilient material havinggood sound transmitting properties and having the free end of one legfirmly engaged and locked between the nut 61 and the wide flat portionof the heat insulating material which abuts the inner face of thehousing wall 53. The free end of the other leg of drive member 62 issecured to the armature of the transducer 60. The drive member 62 isthus rigidly affixed to the rear wall 53 of housing 52, while theinsulating material 55 isolates the mounting screw 59 and prevents anyheat generated by the tested section 54 from reaching the transducer 60.Mounted on an end face of the housing 52 is a two terminal socket member64, the terminals of which are connected by a double lead Wire 63 to theoutput terminals of the transducer 60. Each of the pickups 51 isconnected to a corresponding socket 43 by along, preferably coaxialcable 66 provided at opposite ends with plugs or jacks which engagerespective pairs of sockets 43 and 64, as shown in FIG. 1.

It will. be appreciated that the L-shaped drive member 62. supports thetransducer 60 in cantelever fashion, so that the transducer is in effectfloating within the housing 52. Sound waves emitted by the member beingtested are transmitted through the magnet 56 and housing 52 to the drivemember 62 and the connected transducer crystal, causing responsivevibration thereof. The floating housing of transducer 60, however, issubject to inertia, and the relative movement of the drive member 62 andthe transducer housing at opposite ends of the crystal, causes thelatter to convert the aforementioned sound waves into electricalimpulses which are fed through cable 66 to the amplifier circuit. Toprevent the reception and amplifica tion of ambient sound waves whichmay mask the sound waves received directly, the housing 52 may be filledwith a sound-insulating material 65 such as polyurethane foam.Alternately, a vacuum may be produced within the housing 52.

One or more of the pickup members which may be employed with the presentapparatus for reaching and sensing areas which are not easily ornormally accessible to the pickups 51 may be of the type illustrated inFIG. 5 of the drawing and differs from the pickup 51 in that anelongated probe is substituted for the magnet 56. Specifically, thepickup 67 includes a housing 68 which supports a socket 69 and in whicha transducer 75 is located. The transducer 75 is also of theconventional crystal type of different design than the transducer 60.There is provided an elongated, preferably metal, probe 70, pointed atits leading end 71 and provided at its trailing end with a coaxialthreaded shank 72 of reduced transverse cross-section. The shank 72registers with an opening formed in the bottom wall 73 of the housing 68and carries washers located adjacent opposite faces of the wall 73. Theshank 70 is rigidly affixed to the wall 73 by a nut 74 which engages theshank 72. A U-shaped flexible coupling drive member 76, corresponding tothe drive member 63, connects the transducer 75 to the probe 70 andsupports the transducer within the housing 68. The transducer isconnected by leads 79 to the socket 69 mounted on the housing 68 whichsocket is engaged by a plug at one end of a cable, the other end of thecable being provided with a plug which engages a respective socket 43. Amechanical sonic coupling between the transducer of the pickup 67 and asection 78 of the equipment under test is effected merely by engagingthe surface of the section 78 with the probe tip 71. A filling ofsound-insulating material 80 may again be provided in housing 68.

By critical selection of the crystals, drive members and other componentparts of the pick-ups 51 and 67, all of the pick-ups are matched to theamplifier and to each other. Each is, therefore, equally capable ofconverting the sound originating directly at its location into a preciseamplified audible or visual signal, so that two or more pickups locatedat different points on a machine or system can provide an accuratecomparison of sound conditions :at the two points.

Considering now the general application and operation of the apparatusdescribed above, a plurality of pickups 51 are mounted in differentsections of the equipment under test by means of the respective magnets56 and are each connected to the socket 43 by means of cables 66. Theequipment sections receiving the pickups 51 are those providing the mostinformative sound patterns related to the functioning of the equipmentand depend on the type of equipment under test and the nature of themalfunctioning and are readily determined by one skilled in the art. Aset of earphones 46 is coupled to the apparatus by way of a socket 47and the amplifier energized by closing the switch S1, and the switch S3is thrown to the position shown in FIG. 6. The equipment under test isthen brought to its operating state and the optimum tone and volume ofthe sound output of the earphones 46 are effected by adjusting thepotentiometer P and the switch S4. The operator, while listening in onthe earphones 46 and observing the sound level on the meter M,manipulates the switch S2 to successively connect differently locatedindividual pickups 51 to the amplifier input. He is thus capable ofaccurately comparing with high resolution the sound patterns andover-all sound intensities at different parts of the equipment whichinformation enables him to identify and isolate any defect or cause orsource of malfunctioning in the equipment. A greater resolution and thusmore informative data may be obtainable by a complete analysis of thevarious wave forms and these may be obtained by means of anoscilloscope, recording oscillograph or the like whose input isconnected to the binding posts 49. In the same manner, the input of atape recorder may be connected to the binding posts 49, and comparativesound waves recorded on tape for subsequent analysis in a laboratory orthe like. Where a critical sensing area of the equipment under test isunaccessible with the pickup 51, the probe type pickup 67 may be coupledto one of the sockets 43 and employed in the manner described above.

FIG. 1 shows by way of example, two pickups 51 magnetically coupled tosections 54 which may be cylinders of a hydraulic lift. Defects in suchhydraulic lift systems often occur when a burr on the inner surface ofone cylinder causes the piston to fiap away in passing, and thehydraulic fiuid to flow around the piston. While such defect may besuspected from improper performance of the system, isolation of itslocation has been ditlicult, if not impossible. Assuming that suchcondition exists in one of the cylinders 54 shown in FIG. 1, the pickups51 can be utilized to locate the source of the malfunction. With thepickups coupled to the two cylinders as shown, and the operatorlistening on the earphones 46, the knob 50 of selector switch S2 isturned back and forth to connect each pickup 51 alternately andsuccessively to the amplifier input. By comparison of the two sounds,the operator should be readily able to detect the sound of themalfunction, and thus identify the defective cylinder. By means of themagnet 56, the pickup 51 may now he slid progressively over the surfaceof the defective cylinder, with the comparison switching continued ateach location, until the precise position of the defect is located.Since each of the magnets 56 not only acts as a mechanical couplingmeans but as the sound sensor or audio coupling as well, the sounddetected by the pickup is restricted to that eminating from the areadirectly beneath the magnet, and each pickup is, therefore, capable ofisolating sound sources to a high degree.

Where a team of inspectors is testing a piece of equipment, each memberof the team is provided with a pair of earphones 46 connected to theamplifier output. Communication between the members of the team isreadily effected by reversing the switch S3 from the position shown inFIG. 6 to thereby decouple the pickups 51 and 67 from the amplifierinput and coupling the microphones 45 thereto. In this manner, theinspector at the control panel can instruct an operator at a remotelocation regarding placement and movement of the pickups for optimumcomparison determination. The apparatus thus assumes the role of anintercommunication system between the team members using the microphonesand earphones 45 and 46, The apparatus is returned to its test state byreversing the switch S3 to its original position as shown in FIG. 6. Thecondition of the battery B is determined by merely momentarily closingthe switch S with the switch S1 open and the reading on the meter M isan indication of the condition of the battery B.

In order to store or transport the apparatus 10, the various pickups,microphones, earphones and accessories are detached and uncoupled andplaced in the storage space 28 through the rear opening thereto and thelid 34 is then closed. The pickup members 51 may be stored in thismanner by merely applying their magnets 56 to the metal walls of thestorage space 28.

The apparatus described herein may be employed in picking up andcomparing the opening and closing of drift valves and other types ofautomatic valves, detecting and amplifying the sound of dirt particlesin oil surrounding encased bearings, detecting the sound of springsexpanding and contracting in brake drums, reproducing other soundsheretofore incapable of isolation.

While there have been described and illustrated preferred embodiments ofthe present invention, it is apparent that numerous alterations,omissions and additions may be made wi.hout departing from the spiritand scope thereof.

What I claim is:

1. A test apparatus for the comparison of sound emitted at differentareas of equipment under test, said apparatus comprising a control unitincluding an audio amplifier having an input and an output, a pluralityof remote, individual audio pickup devices each comprising a couplingmember for releasably mounting said pickup device on said equipmentunder test, a transducer element, and a flexible drive membermechanically coupling said transducer element and said coupling memberwith said coupling member also serving as a sensor to transmit soundwaves from said equipment under test through said drive member to saidtransducer element, means including a manually-operable switch on saidcontrol unit for selective, alternate and successive coupling of saidindividual pickup devices to said amplifier input, and means forconnecting earphones and a current meter across said amplifier output,whereby to provide audible and visual comparison of sound emitted atspaced points on said test equipment when said pickup devices aremounted respectively at said spaced points and said switch is manuallymanipulated to alternately and successively couple said pickup devicesto said amplifier input.

2. A test apparatus according to claim 1 in which each pickup devicealso includes a housing containing said transducer element, and meanssecuring said coupling member rigidly to said housing and to one end ofsaid drive member, with said transducer mounted on the other end of saiddrive member and being otherwise unsupported.

3. A test apparatus according to claim 2 in which said housing is filledwith sound-insulating material capable of shielding said transducer fromabient sound waves,

4. A test apparatus according to claim 2 which also includes heatinsulating material interposed between said drive member and saidcoupling member and housing for shielding said transducer element fromheat emitted by the equipment under test.

5. A test apparatus according to claim 2 in which said coupling membercomprises a permanent magnet.

6. A test apparatus according to claim 5 in which said magnet has fourintegral projecting legs serving as pole sections and arranged fornon-slip magnetic coupling to a curved surface of said equipment to betested.

7. A test apparatus according to claim 1 in which said control unit alsoincludes terminal means adapted for connection to a microphone, andswitch means for selective connection of said terminal means to theinput of said audio amplifier.

8. A test apparatus according to claim 1 in which said control unitincludes means for connecting an oscilloscope and tape recorder to theoutput of said audio amplifier.

9. A test apparatus according to claim 1 in which said control unitcomprises a portable housing, a face panel releasably mounted on saidhousing and mounting said audio amplifier, manually-operable switch, andcurrent meter, a power source battery within said control unit housing,and switch means connecting said battery to said amplifier.

10. A test apparatus according to claim 9 in which said manuallyoperable switch is a multicontact rotary switch mounted on said facepanel and including a selector arm connected to said amplifier input anda plurality of input terminals, said face plate having a plurality ofsockets mounted thereon, each socket being connected to a respectivetreminal of said selector switch, each of said audio pickup deviceshaving a connecting cable terminating in a plug sized for reception inone of said sockets.

References Cited UNITED STATES PATENTS 1,725,872 8/1929 Lawrence 73-71.4XR 2,826,706 3/1958 Sackett 7371.2 XR 2,848,558 8/1958 Poulton 310- XR3,115,616 12/1963 Parris 73 71.4 XR 3,146,360 8/1964 Marshall 310-89 XR3,254,528 6/1966 Michael 7371.4

FOREIGN PATENTS 1,021,172 11/1952 France.

JAMES J. GILL, Primary Examiner.

1. A TEST APPARATUS FOR THE COMPARISON OF SOUND EMITTED AT DIFFERENTAREAS OF EQUIPMENT UNDER TEST, SAID APPARATUS COMPRISING A CONTROL UNITINCLUDING AN AUDIO AMPLIFIER HAVING AN INPUT AND AN OUTPUT, A PLURALITYOF REMOTE, INDIVIDUAL AUDIO PICKUP DEVICES EACH COMPRISING A COUPLINGMEMBER FOR RELEASABLY MOUNTING SAID PICKUP DEVICE ON SAID EQUIPMENTUNDER TEST, A TRANSDUCER ELEMENT, AND A FLEXIBLE DRIVE MEMBERMECHANICALLY COUPLING SAID TRANSDUCER ELEMENT AND SAID COUPLING MEMBERWITH SAID COUPLING MEMBER ALSO SERVING AS A SENSOR TO TRANSMIT SOUNDWAVES FROM SAID EQUIPMENT UNDER TEST THROUGH SAID DRIVE MEMBER TO SAIDTRANSDUCER ELEMENT, MEANS INCLUDING A MANUALLY-OPERABLE SWITCH ON SAIDCONTROL UNIT FOR SELECTIVE, ALTERNATE AND SUCCESSIVE COUPLING OF SAIDINDIVIDUAL PICKUP DEVICES TO SAID AMPLIFIER INPUT, AND MEANS FORCONNECTING EARPHONES AND A CURRENT METER ACROSS SAID AMPLIFIER OUTPUT,WHEREBY TO PROVIDE AUDIBLE AND VISUAL COMPARISON OF SOUND EMITTED ATSPACED POINT ON SAID TEST EQUIPMENT WHEN SAID PICKUP DEVICES ARE MOUNTEDRESPECTIVELY AT SAID SPACED POINTS AND SAID SWITCH IS MANUALLYMANIPULATED TO ALTERNATELY AND SUCCESSIVELY COUPLE SAID PICKUP DEVICESTO SAID AMPLIFIER INPUT.